1. Field of the Invention
The present invention relates to a burner for jetting a fuel and a gasifying agent (a gas including at least one of oxygen, hydrogen and steam) into an apparatus for gasifying an organic fuel like coal etc., and to a fuel etc. supply method.
2. Description of the Prior Art
FIG. 15 is a diagrammatic view showing an arrangement of gasifier and ancillary machinery and equipment in the prior art. Coal, crushed at a mill 46 and mixed with N.sub.2 gas at a mixer 47, is carried by the N.sub.2 gas and charged into a coal burner 011 for a gasifier 41. The coal is reacted with a gasifying agent so as to be gasified, and then is separated of char at a char recovery device 42. The coal is then taken out as a generated gas. The separated char enters a mixer 45 and is returned to a char burner 011 for the gasifier 41 by a carrying gas N.sub.2 to be burnt by the gasifying agent.
FIG. 16 is a longitudinal sectional view showing one example of a burner in the prior art which charges a fuel and a gasifying agent into a gasifier. The gasifying agent flows in a central passage 012, formed in the center of an inner tube 032. A mixture of the fuel (pulverized coal) and a carrying N.sub.2 flows in an annular sectional passage 013, formed between the inner tube 032 and an outer tube 031. The central passage 012 and annular sectional passage 013 are disposed coaxially. A fuel jet 01, 03 and a gasifying agent jet 02, 04 impinge on each other outside the burner, thereby accelerating the mixing of the fuel and the gasifying agent.
In the burner of the prior art in which the fuel jet and the gasifying agent jet impinge on each other outside the burner, if the oxygen partial pressure of the gasifying agent is low, then the combustion speed of the fuel and char becomes smaller than the jet velocity in the close vicinity of burner. Therefore, the ignition point becomes remote from the jetting port of the burner. In a combustor portion of a coal gasifier, there occur shortcomings, such as a worsening of combustibility due to a remote ignition point, and a solidification of ash melted in the burner portion.
As to carrying by nitrogen, the charging amount of nitrogen into the gasifier is preferably reduced as much as possible for the performance of the gasifier. However, in a coaxial type burner, if the charging amount of nitrogen is reduced, the size of the gap between the annular sectional passages in which the fuel flows is made smaller for geometrical reasons, and then a possibility of blockage arises.
In order to obtain a good ignition of fuel, it is necessary to adjust the flow rate of the fuel, char, and the premixing gas, corresponding to calorific value and reaction speed of the fuel, and to set a most appropriate condition for ignition. Conventionally, if the fuel and char are carried by an inert gas such as nitrogen etc., they are mixed with a gasifying agent in the gasifier (but outside the burner) so that the ignition condition is satisfied. If the oxygen partial pressure in the gasifying agent is low, however, the reaction of the fuel and char at the mixing portion close to the burner jetting port is minimal. Therefore, it is difficult to satisfy a condition for stable ignition.